The annual yield of organic wastes, including human and animal excreta, food wastes, sludge from sewage treatment plants, rotten fruits and vegetables from fruit and vegetable markets and the like, is 10 times of the annual yield of industrial solid wastes. The organic wastes are of large amount and high concentration, which will bring severe environmental pollution if they are not treated in time.
Composting treatment (aerobic fermentation) of organic wastes can achieve recycling utilization of wastes, which is hence widely applied. Various aerobic fermentation reactors have been designed to improve the efficiency of aerobic fermentation, and decrease manufacturing costs of the fermentation devices and operating costs.
The existing aerobic fermentation devices are mainly horizontal type or vertical type. Chinese patent No. CN 1100024 C discloses a horizontal-type aerobic fermentation reactor with a horizontal-slot structure. The reactor and materials to be fermented are heated by hot oil. The materials to be fermented are stirred by mixing blades so as to realize pile turning and oxygen supply. However, an upper surface of this reactor is too large to insulate heat, and hence the energy consumption is very huge. The materials to be fermented will easily produce fouling on the inner wall of the fermenter, which makes it difficult for the hot oil to conduct heat. The fouling may be reduced by increasing the number of mixing blades, however too much mixing blades may increase energy consumption. Moreover, in this Chinese patent, it is hard for fermented products to be discharged, since the mixing blades are helpless for discharging, and hence the fermented products are manually discharged.
Chinese patent No. 95119800.9 discloses a horizontal aerobic fermentation reactor with a horizontal-slot structure. The reactor and materials to be fermented are heated by an electrical heater. The materials to be fermented are stirred by screw wing so as to realize pile turning and oxygen supply. However, an upper surface of this reactor is too large to insulate heat. The materials to be fermented are easily compacted by spiral rotation, the air in materials is hence forced out causing anaerobic reaction in which toxic gases such as hydrogen sulfide may be generated, and the aerobic reaction is endangered. The energy consumption for switching between positive and negative directions of spiral rotation is very large, and the device is easily broken down. Moreover, the fermented products are manually discharged under poor dirty working condition.
Chinese patent No. CN 102757270 B discloses a horizontal aerobic fermentation reactor with a horizontal rolling structure. This reactor solves the problems of heating, heat preservation, air intake and outtake, material feed and discharge, and so on. However, its disadvantage is that the materials to be fermented are easily produced fouling on the inner wall of the fermenter, which affects heat conduction.
Chinese utility model No. CN 201933029 U discloses a vertical aerobic fermentation reactor. The materials to be fermented in a lower part of the reactor are easily compacted by the materials in an upper part of the reactor, which makes it hard for the materials to be fermented in the lower part to contact with air. Accordingly, the fermentation is non-uniform, which easily causes anaerobic reaction to produce toxic gases such as hydrogen sulfide.
Chinese patent No. 03821392.3 discloses a vertical aerobic fermentation reactor. In this invention, the problem that the materials in the lower part are compacted is well solved by providing a processing area in the vertical composting device. However, this device is big and tall, the energy consumption for turning over the materials in the processing area is huge, and the manufacturing and operational costs are very expensive.